Current Sensor Having A Flux Concentrator For Redirecting A Magnetic Field Through Two Magnetic Field Sensing Elements

ABSTRACT

A method can use a current sensor that can include a magnetic flux concentrator and a first magnetic field sensing element disposed proximate to the magnetic flux concentrator, the first magnetic field sensing element having a first maximum response axis, the first magnetic field sensing element operable to generate a first signal responsive to a first magnetic field proximate to the first magnetic field sensing element resulting from an electrical current passing through a conductor, wherein the magnetic flux concentrator is operable to influence a direction of the first magnetic field. The current sensor also includes a second magnetic field sensing element disposed proximate to the magnetic flux concentrator, the second magnetic field sensing element having a second maximum response axis, the second magnetic field sensing element operable to generate a second signal responsive to a second magnetic field proximate to the second magnetic field sensing element resulting from the electrical current passing through the conductor, wherein the magnetic flux concentrator is operable to influence a direction of the second magnetic field. The current sensor can also include a differencing circuit operable to subtract the first and second signals to generate a difference signal related to the electrical current.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

FIELD OF THE INVENTION

This invention relates generally to current sensors and, moreparticularly, to a current sensor that has a magnetic flux concentratorfor redirecting a magnetic field through two magnetic field sensingelements, e.g., two planar Hall elements.

BACKGROUND

A magnetic field sensor can be used to sense a magnetic field generatedby an electrical current flowing through a conductor. These magneticfield sensors can be referred to as current sensors.

Referring to FIG. 1, a typical current sensor assembly 100 has a ringshaped magnetic flux concentrator 104 disposed around a conductor 102 ofelectrical current. As is known, a current, represented by an arrow 106,flowing through the conductor 102 has a magnetic field circular aroundthe conductor, with a magnetic direction determined by a direction ofthe electrical current. The magnetic flux concentrator 104 can cause anincrease (a concentration) of the magnetic field proximate to and withinthe magnetic flux concentrator 104. The magnetic flux concentrator 104can also result in some amount of desirable reduction in sensitivity tostray external magnetic fields.

The magnetic flux concentrator 104 can include a gap in a region 110, inwhich a magnetic field sensor 108 (i.e., a current sensor) can bedisposed. In operation, in response to the current flowing through theconductor 102, which generates a concentrated magnetic field in themagnetic flux concentrator 104, the increased magnetic field essentiallypasses though the gap within the region 110, also with an increasedmagnetic field. The current sensor 108 can be responsive to magneticfields in the z-direction in x-y-z Cartesian coordinates.

The circular magnetic flux concentrator 104 can be relatively large andrelatively expensive.

Without having the circular magnetic flux concentrator, the currentsensor 108 would generate insufficient sensitivity to the sensedcurrent, would provide insufficient signal to noise ratio, and wouldprovide an insufficient decrease of sensitivity to stray externalmagnetic fields.

It would also be desirable to provide a current sensor that does not usea circular magnetic flux concentrator but that can generate a sufficientsensitivity, can provide sufficient signal to noise ratio, and canprovide a sufficient decrease of sensitivity to stray external magneticfields.

SUMMARY

The present invention provides a current sensor that does not use acircular magnetic flux concentrator but that can generate a sufficientsensitivity, can provide sufficient signal to noise ratio, and canprovide a sufficient decrease of sensitivity to stray external magneticfields.

In accordance with an example useful for understanding an aspect of thepresent invention, a current sensor can include a magnetic fluxconcentrator and a first magnetic field sensing element disposedproximate to the magnetic flux concentrator, the first magnetic fieldsensing element having a first maximum response axis, the first magneticfield sensing element operable to generate a first signal responsive toa first magnetic field proximate to the first magnetic field sensingelement resulting from an electrical current passing through aconductor, wherein the magnetic flux concentrator is operable toinfluence a direction of the first magnetic field. The current sensoralso includes a second magnetic field sensing element disposed proximateto the magnetic flux concentrator, the second magnetic field sensingelement having a second maximum response axis, the second magnetic fieldsensing element operable to generate a second signal responsive to asecond magnetic field proximate to the second magnetic field sensingelement resulting from the electrical current passing through theconductor, wherein the magnetic flux concentrator is operable toinfluence a direction of the second magnetic field. The current sensorcan also include a differencing circuit operable to subtract the firstand second signals to generate a difference signal related to theelectrical current.

In accordance with another example useful for understanding anotheraspect of the present invention, a method of measuring an electricalcurrent can include providing a first magnetic field sensing elementdisposed proximate to a magnetic flux concentrator, the first magneticfield sensing element having a first maximum response axis. The methodalso includes providing a second magnetic field sensing element disposedproximate to the magnetic flux concentrator, the second magnetic fieldsensing element having a second maximum response axis. The method canalso include using the first magnetic field sensing element to generatea first signal responsive to a first magnetic field proximate resultingfrom the electrical current passing through a conductor, wherein themagnetic flux concentrator is operable to influence a direction of thefirst magnetic field. The method can also include using the secondmagnetic field sensing element to generate a second signal responsive toa second magnetic field resulting from the electrical current passingthrough the conductor, wherein the magnetic flux concentrator isoperable to influence a direction of the second magnetic field. Themethod can also include, with a differencing circuit, subtracting thefirst and second signals to generate a difference signal related to theelectrical current.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention, as well as the invention itselfmay be more fully understood from the following detailed description ofthe drawings, in which:

FIG. 1 is a pictorial showing a conventional current sensor arrangementhaving a circular magnetic flux concentrator;

FIG. 2 is a block diagram showing a side view of a current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 3 is a block diagram of a portion of an integrated current sensorhaving two planar Hall elements coupled to an electronic circuitresulting in a differential arrangement, which can be used as a portionof a current sensor according to the current sensor arrangements ofFIGS. 2 and 4-14 herein;

FIG. 4 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 5 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 6 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 7 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 8 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 9 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 10 is a block diagram showing a side view of another current sensorarrangement with two planar Hall elements and a magnetic fluxconcentrator, all disposed proximate to a bus bar conductor operable topass an electrical current;

FIG. 11 is a block diagram of a current sensor having two planar Hallelements and an electronic circuit disposed on or within a substrate,the substrate disposed upon a first surface of a lead frame, and amagnetic flux concentrator disposed upon a second surface of thesubstrate, and an enclosure surrounding the substrate, a portion of thelead frame, and the magnetic flux concentrator;

FIG. 12 is a block diagram of another current sensor having two planarHall elements and an electronic circuit disposed on or within asubstrate, the substrate disposed upon a first surface of a lead frame,an enclosure surrounding the substrate and a portion of the lead frame,and a magnetic flux concentrator disposed over the enclosure;

FIG. 13 is a perspective drawing showing a solid magnetic fluxconcentrator disposed proximate to positions of two planar Hallelements, the magnetic flux concentrator disposed over a bus barconductor; and

FIG. 14 is a perspective drawing showing a laminated magnetic fluxconcentrator disposed proximate to positions of two planar Hallelements, the magnetic flux concentrator disposed over a bus barconductor; and

FIG. 15 is a block diagram of another current sensor having twomagnetoresistance elements and an electronic circuit disposed on orwithin a substrate, the substrate disposed upon a first surface of alead frame, and a magnetic flux concentrator disposed proximate to thesubstrate.

DETAILED DESCRIPTION

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing element can be, but is not limited to,a Hall effect element, a magnetoresistance element, or amagnetotransistor. As is known, there are different types of Hall effectelements, for example, a planar Hall element, a vertical Hall element,and a Circular Vertical Hall (CVH) element. As is also known, there aredifferent types of magnetoresistance elements, for example, asemiconductor magnetoresistance element such as Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, for example, a spinvalve, an anisotropic magnetoresistance element (AMR), a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).The magnetic field sensing element may be a single element or,alternatively, may include two or more magnetic field sensing elementsarranged in various configurations, e.g., a half bridge or full(Wheatstone) bridge. Depending on the device type and other applicationrequirements, the magnetic field sensing element may be a device made ofa type IV semiconductor material such as Silicon (Si) or Germanium (Ge),or a type III-V semiconductor material like Gallium-Arsenide (GaAs) oran Indium compound, e.g., Indium-Antimonide (InSb).

As is known, some of the above-described magnetic field sensing elementstend to have an axis of maximum sensitivity parallel to a substrate thatsupports the magnetic field sensing element, and others of theabove-described magnetic field sensing elements tend to have an axis ofmaximum sensitivity perpendicular to a substrate that supports themagnetic field sensing element. In particular, planar Hall elements tendto have axes of sensitivity perpendicular to a substrate, while metalbased or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) andvertical Hall elements tend to have axes of sensitivity parallel to asubstrate.

As used herein, the term “magnetic field sensor” is used to describe anassembly that uses a magnetic field sensing element in combination withan electronic circuit, all disposed upon a common substrate, e.g., asemiconductor substrate. Magnetic field sensors are used in a variety ofapplications, including, but not limited to, an angle sensor that sensesan angle of a direction of a magnetic field, a current sensor thatsenses a magnetic field generated by a current carried by acurrent-carrying conductor, a magnetic switch that senses the proximityof a ferromagnetic object, a rotation detector that senses passingferromagnetic articles, for example, magnetic domains of a ring magnetor a ferromagnetic target (e.g., gear teeth) where the magnetic fieldsensor is used in combination with a back-biased or other magnet, and amagnetic field sensor that senses a magnetic field density of a magneticfield.

The terms “parallel” and “perpendicular” are used in various contextsherein. It should be understood that the terms parallel andperpendicular do not require exact perpendicularity or exactparallelism, but instead it is intended that normal manufacturingtolerances apply, which tolerances depend upon the context in which theterms are used. In some instances, the term “substantially” is used tomodify the terms “parallel” or “perpendicular.” In general, use of theterm “substantially” reflects angles that are beyond manufacturingtolerances, for example, within +/−ten degrees.

While electronic circuits shown in figures herein may be shown in theform of analog blocks or digital blocks, it will be understood that theanalog blocks can be replaced by digital blocks that perform the same orsimilar functions and the digital blocks can be replaced by analogblocks that perform the same or similar functions. Analog-to-digital ordigital-to-analog conversions may not be explicitly shown in thefigures, but should be understood.

As used herein, the term “amplifier” is used to describe a circuitelement with a gain greater than one, less than one, or equal to one.

As used herein, the terms “line” and “linear” are used to describeeither a straight line or a curved line. The line can be described by afunction having any order less than infinite.

Many examples shown and described herein use planar Hall elements.Magnetic flux concentrators shown and described herein can redirectmagnetic fields to pass through the planar Hall elements in a directionto which they are sensitive, i.e., such that a component of thedirection is perpendicular to a substrate on which the planar Hallelements are formed. However, as described in conjunction with FIG. 15,in other embodiments, other types of magnetic field sensing elements canbe used, for example, vertical Hall elements or magnetoresistanceelements, which can be disposed upon substrates oriented ninety degreesfrom those shown, such that they are responsive to the redirectedmagnetic fields.

Referring to FIG. 2, an example of a current sensor arrangement 200 caninclude first and second planar Hall elements 208, 210, respectively,disposed proximate to a bus bar (rectangular) conductor 202, here shownto be a bus bar (rectangular) conductor 202, can be operable to conductan electrical current 204, here coming out of the page.

A magnetic flux concentrator 212 disposed proximate to the conductor 202has a channel 214 parallel to an x-axis and oriented toward theconductor 202. The first and second planar Hall elements 208, 210 can bedisposed between the conductor 202 and the magnetic flux concentrator212.

A flux line 206 can be one of many flux lines, for which each respectiveflux line is indicative of a particular respective magnitude of magneticfield. Thus, each flux line is essentially an isoline having the samemagnetic field. Arrows along the flux line 206 can be indicative of adirection of the magnetic field.

For a direction of the current 204 coming out of the page, the magneticflux line 206 has a magnetic direction generally counterclockwise. Ifthe current 204 flowed in the opposite direction, then the magnetic fluxline 206 would have a magnetic direction generally clockwise.

In operation, the magnetic flux concentrator 212 tends to redirect theflux line upward and then downward into and out of the magnetic fluxconcentrator 212. With this redirection, the flux line 206 passesthrough the first and second planar Hall elements 208, 210 withdirection components substantially parallel to a z direction to whichthe first and second planar Hall elements 208, 210 are responsive, butwith opposite directions. Thus, the first and second planar Hallelements 208, 210 have opposite responses to the flux line 206, andtherefore, opposite responses to the current 204. The redirection andresulting opposite responses by the first and second planar Hallelements 208, 210 can be used advantageously in the electronic circuit300 of FIG. 3.

Referring now to FIG. 3, a portion 300 of a current sensor can includefirst and second planar Hall elements 304, 314 coupled to an electroniccircuit 301. The first and second planar Hall elements 304, 314 can becoupled between a voltage source 302 and a ground.

The first planar Hall element 304 can generate a first differentialsignal 304 a, 304 b and the second planar Hall element can generate asecond differential signal 314 a, 314 b.

For discussion above, it should be understood that, when arranged as inFIG. 2, the first differential signal 304 a, 304 b and the seconddifferential signal 314 a, 314 b can be opposite signals, e.g., signalswith opposite voltages.

As is known, a typical planar Hall element is a four terminal device,often square in shape from a top view, and thus, having four corners. Avoltage and ground are applied to a pair of diagonally opposingterminals, respectively, and a differential voltage is generated acrossthe other pair of diagonally opposing terminals.

In some arrangements, and in order to reduce a DC offset voltage(voltage indicative of a magnetic field when no magnetic field ispresent), the pair of terminals selected for coupling to the voltage andground, and the pair of terminals selected for the differential signalfrom the Hall element changes from time to time, generally at a highrate of change. There are four such coupling arrangements for a planarHall element. When operating, the coupling arrangements can be referredto as current spinning.

Accordingly, the electronic circuit 301 can include a first currentspinning circuit 306 coupled to receive the first differential signal304 a, 304 b, which can come from first selected pairs of terminals ofthe first planar Hall element. Not shown, the first current spinningcircuit 306 can also control to which second pairs of terminals of thefirst planar Hall element 304 the voltage 302 and ground are coupled insynchronous relationship with the first pairs of terminals.

The first current spinning circuit 306 can generate a first spinningsignal 306 a. With the current spinning arrangement, the first spinningsignal can have two or more spectral parts, for which a desired basebandpart can be indicative of a magnetic field sensed by the first planarHall element 304 and a second higher frequency part can be indicative ofthe DC offset voltage.

The spinning signal 306 a can be coupled to a low pass filter operableto generate a first filtered signal 308 a that can include only thedesired baseband part.

Elements 316 and 318 can operate in the same way as elements 306, 308,and can result in a second filtered signal 318 a.

A differencing circuit 310 can be coupled to the first and secondfiltered signals 308 a, 318 a, respectively, and can be operable togenerate a difference signal 310 a.

An amplifier 312 can be coupled to the difference signal 310 a and canbe operable to generate an amplified difference signal 312 a.

It should be appreciated that, because the magnetic fields pass throughthe first and second planer Hall elements, 208, 210 of FIG. 2 inopposite direction, and therefore generate opposite signals, thedifferencing circuit 310 operates to combine the first and secondfiltered signals 308 a, 318 a constructively.

It should also be appreciated that a stray magnetic field generatedoutside of the current sensor arrangement 200 can received by the firstand second planar Hall elements 208, 210 in the same direction, andtherefore generate same stray field related signals with the same phaseor sign. Same stray field related signals generated by the first andsecond planar Hall element 208, 210 result in a cancellation of the samestray field related signals by the differencing circuit 310.

In other embodiments, current spinning is not used and the currentspinning circuits 306, 316 and perhaps the low pass filters 308, 318,can be omitted.

The first and second planar Hall elements 304, 314 and the electroniccircuit 301 can be used in the current sensor arrangements of FIGS. 2and 4-14 herein.

Referring now to FIG. 4, another illustrative current sensor arrangement400 can be like the current sensor arrangement of FIG. 2. A conductor402 can carry an electrical current (into and/or out of the page),resulting in flux lines 404. A magnetic flux concentrator 410 can bedisposed substantially symmetrically with the conductor 402.Essentially, the magnetic flux concentrator 410 has a central plane(parallel to the x-z plane) bisecting the magnetic flux concentrator410, wherein the magnetic flux concentrator 410 is symmetrical aroundthe central plane, and wherein the first and second planar Hall elements406, 408 are disposed symmetrically on opposite sides of the centralplane.

The magnetic flux concentrator 410 can have a relative magneticpermeability of greater than about two. The relative magneticpermeability μr is defined as such: μr=μ/μ₀. Where μ is the magneticpermeability of the magnetic flux concentrator and μ₀ is the magneticpermeability of free space.

The first and second planar Hall elements 406, 408 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 410 and the first and second planar Hallelements 406, 408 are disposed proximate to a face 402 a, e.g., alargest face, of the conductor 402, which is parallel to an x-y plane.

As shown, and similar to that shown in FIG. 2, flux lines 404 atpositions of the first and second planar Hall elements 406, 408 areredirected by the magnetic flux concentrator 410 to have directions thatare parallel to, or that have direction components parallel to, thez-axis. As understood from FIG. 2 above, the direction componentsparallel to the z-axis are opposite in direction at the two planar Hallelements. 406, 408.

The magnetic flux concentrator 410 has two faces 410 b, 410 c parallelto the x-z plane that are rectangular, and a face 410 a parallel to thex-y plane that is rectangular. However, the magnetic flux concentrator410 has a side 410 d parallel to the x-y plane that has a rectangularchannel 412 running parallel to an x-direction.

The current sensor arrangement 400 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement, e.g., the currentsensor arrangement 100 of FIG. 1.

Referring now to FIG. 5, another illustrative current sensor arrangement500 can be like the current sensor arrangement of FIG. 2. A conductor502 can carry an electrical current (into and/or out of the page),resulting in flux lines 504. A magnetic flux concentrator 510 can bedisposed symmetrically with the conductor 502. Essentially, the magneticflux concentrator 510 has a central plane (parallel to the x-z plane)bisecting the magnetic flux concentrator 510, wherein the magnetic fluxconcentrator 510 is symmetrical around the central plane, and whereinthe first and second planar Hall elements 506, 508 are disposedsymmetrically on opposite sides of the central plane.

The magnetic flux concentrator 450 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 506, 508 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 510 and the first and second planar Hallelements 506, 508 are disposed proximate to a largest face 502 a of theconductor 502, which is parallel to an x-y plane.

As shown, and similar to that shown in FIG. 2, flux lines 504 atpositions of the first and second planar Hall elements 506, 508 areredirected by the magnetic flux concentrator 510 to have directions thatare parallel to, or that have direction components parallel to, thez-axis. As understood from FIG. 2 above, the direction componentsparallel to the z-axis are opposite in direction but have substantiallythe same amplitude.

The magnetic flux concentrator 510 has two faces 510 b, 510 c parallelto the x-z plane that are rectangular, and a face 510 a parallel to thex-y plane that is rectangular. A side 510 d parallel to the x-y plane isalso rectangular. Thus, the magnetic flux concentrator 510 is arectangular solid.

The current sensor arrangement 500 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement.

Referring now to FIG. 6, another illustrative current sensor arrangement600 can be like the current sensor arrangement of FIG. 2. A conductor602 can carry an electrical current (into and/or out of the page),resulting in flux lines 604. A magnetic flux concentrator 610 can bedisposed symmetrically with the conductor 602. Essentially, the magneticflux concentrator 610 has a central plane (parallel to the x-z plane)bisecting the magnetic flux concentrator 610, wherein the magnetic fluxconcentrator 610 is symmetrical around the central plane, and whereinthe first and second planar Hall elements 606, 608 are disposedsymmetrically on opposite sides of the central plane.

The magnetic flux concentrator 610 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 606, 608 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 610 and the first and second planar Hallelements 606, 608 are disposed proximate to a largest face 602 a of theconductor 602, which is parallel to an x-y plane.

As shown, and similar to that shown in FIG. 2, flux lines 606 atpositions of the first and second planar Hall elements 606, 608 areredirected by the magnetic flux concentrator 610 to have directions thatare parallel to, or that have direction components parallel to, thez-axis. As understood from FIG. 2 above, the direction componentsparallel to the z-axis are opposite in direction but have substantiallythe same amplitude.

The magnetic flux concentrator 610 has two faces 610 b, 610 c notparallel to the x-z plane, but that are rectangular, and a face 610 aparallel to the x-y plane that is rectangular. Thus, the magnetic fluxconcentrator 610 has a trapezoidal shape. The magnetic flux concentrator610 has a side 610 d parallel to the x-y plane that has a trapezoidalchannel 612 running parallel to an x-direction.

The current sensor arrangement 600 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement.

Referring now to FIG. 7, another illustrative current sensor arrangement700 can be like the current sensor arrangement of FIG. 2. A conductor702 can carry an electrical current (into and/or out of the page),resulting in flux lines 704. A magnetic flux concentrator 710 can bedisposed symmetrically with the conductor 702. Essentially, the magneticflux concentrator 710 has a central plane (parallel to the x-z plane)bisecting the magnetic flux concentrator 710, wherein the magnetic fluxconcentrator 710 is symmetrical around the central plane, and whereinthe first and second planar Hall elements 706, 708 are disposedsymmetrically on opposite sides of the central plane.

The magnetic flux concentrator 710 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 706, 708 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 710 and the first and second planar Hallelements 706, 708 are disposed proximate to a largest face 702 a of theconductor 702, which is parallel to an x-y plane.

As shown, and similar to that shown in FIG. 2, flux lines 704 atpositions of the first and second planar Hall elements 706, 708 areredirected by the magnetic flux concentrator 710 to have directions thatare parallel to, or that have direction components parallel to, thez-axis. As understood from FIG. 2 above, the direction componentsparallel to the z-axis are opposite in direction but have substantiallythe same amplitude.

The magnetic flux concentrator 710 has two faces 710 b, 710 c parallelto the x-z plane that are rectangular, and a face 710 a parallel to thex-y plane that is rectangular. The faces 710 b, 710 c intersect the face710 a with curved regions. The magnetic flux concentrator 710 has a side710 d parallel to the x-y plane that has a semi-circular channel 712running parallel to an x-direction.

The current sensor arrangement 700 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement.

Referring now to FIG. 8, another illustrative current sensor arrangement800 can be like the current sensor arrangement of FIG. 2. A conductor802 can carry an electrical current (into and/or out of the page),resulting in flux lines 804. A magnetic flux concentrator 810 can bedisposed asymmetrically with the conductor 802. The magnetic fluxconcentrator 810 has a central plane (parallel to the x-z plane)bisecting the magnetic flux concentrator 810, wherein the magnetic fluxconcentrator 810 is symmetrical around the central plane, and whereinthe first and second planar Hall elements 806, 808 are disposedasymmetrically relative to the central plane.

The magnetic flux concentrator 810 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 806, 808 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 810 and the first and second planar Hallelements 806, 808 are disposed proximate to a largest face 802 a of theconductor 802, which is parallel to an x-y plane.

As shown, and similar to that shown in FIG. 2, flux lines 804 atpositions of the first and second planar Hall elements 806, 808 areredirected by the magnetic flux concentrator 810 to have directions thathave direction components parallel to the z-axis. As understood fromFIG. 2 above, the direction components parallel to the z-axis areopposite in direction, and here do not have the same amplitude or angleat the planar Hall elements 806, 808.

The magnetic flux concentrator 810 has two faces 810 b, 810 c parallelto the x-z plane that are rectangular, and a face 810 a parallel to thex-y plane that is rectangular. A side 810 d parallel to the x-y plane isalso rectangular. Thus, the magnetic flux concentrator 810 is arectangular solid.

The current sensor arrangement 800 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement, but not as much as forcurrent sensor arrangements described in other figures herein.

Referring now to FIG. 9, another illustrative current sensor arrangement900 can be like the current sensor arrangement of FIG. 2. A conductor902 can carry an electrical current (into and/or out of the page),resulting in flux lines 904. A magnetic flux concentrator 910 can bedisposed asymmetrically with the conductor 902. Essentially, themagnetic flux concentrator 910 has a central plane (parallel to the x-zplane) bisecting the magnetic flux concentrator 910, wherein themagnetic flux concentrator 910 is symmetrical around the central plane,and wherein the first and second planar Hall elements 906, 908 aredisposed symmetrically on opposite sides of the central plane.

The magnetic flux concentrator 910 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 906, 908 have maximum responseaxes substantially parallel to a z-axis.

The magnetic flux concentrator 910 and the first and second planar Hallelements 906, 908 are disposed proximate to an intersection betweenlargest face 902 a of the conductor 902, which is parallel to an x-yplane, and a smaller face of the conductor 902 b.

As shown, and similar to that shown in FIG. 2, flux lines 904 atpositions of the first and second planar Hall elements 906, 908 areredirected by the magnetic flux concentrator 910 to have directioncomponents parallel to the z-axis. The direction components parallel tothe z-axis are not opposite in direction, but still a differentialarrangement is useful.

The magnetic flux concentrator 910 has two faces 910 b, 910 c parallelto the y-z plane that are rectangular, and a face 910 a parallel to thex-y plane that is rectangular. However, the magnetic flux concentrator910 has a side 910 d parallel to the x-y plane that has a rectangularchannel 912 running parallel to a x-direction.

The current sensor arrangement 900 provides a differential currentsensor for which sensitivity is not substantially increased but aninfluence of external stray magnetic fields is reduced, when compared toa single magnetic field sensing element current sensor arrangement.

Referring now to FIG. 10, another illustrative current sensorarrangement 1000 can be like the current sensor arrangement of FIG. 2. Aconductor 1002 can carry an electrical current (into and/or out of thepage), resulting in flux lines 1004. A magnetic flux concentrator 1010can be disposed symmetrically with the conductor 1002. The magnetic fluxconcentrator 1010 has a central plane (parallel to the x-y plane)bisecting the magnetic flux concentrator 1010, wherein the magnetic fluxconcentrator 1010 is symmetrical around the central plane, and whereinthe first and second planar Hall elements 1006, 1008 are disposedsymmetrically on opposite sides of the central plane.

The magnetic flux concentrator 1010 can have a relative magneticpermeability of greater than about two.

The first and second planar Hall elements 1006, 1008 have maximumresponse axes substantially parallel to and y-axis.

The magnetic flux concentrator 1010 and the first and second planar Hallelements 1006, 1008 are disposed proximate to an intersection proximateto a smallest face 1002 b of the conductor 1002, which is parallel to ax-z plane.

As shown, and similar to that shown in FIG. 2, flux lines 1004 atpositions of the first and second planar Hall elements 1006, 1008 areredirected by the magnetic flux concentrator 1010 to have directioncomponents parallel to the y-axis. The direction components parallel tothe y-axis are opposite in direction.

The magnetic flux concentrator 1010 has two faces 1010 b, 1010 cparallel to the x-y plane that are rectangular, and a face 1010 aparallel to the x-z plane that is rectangular. However, the magneticflux concentrator 1010 has a side 1010 d parallel to the x-z plane thathas a rectangular channel 1012 running parallel to a x-direction.

The current sensor arrangement 1000 provides a differential currentsensor for which sensitivity is increased and an influence of externalstray magnetic fields is reduced, when compared to a single magneticfield sensing element current sensor arrangement.

Unlike the current sensor arrangements described above, for which planarHall elements are disposed over a largest surface of a conductor, herethe planar Hall elements are disposed to the side of a conductor, withsimilar advantageous functions.

The magnetic flux concentrators described herein can be operable toinfluence the direction of the first magnetic field to pass through thefirst planar Hall element in a first direction, the magnetic fluxconcentrator is operable to influence the direction of the secondmagnetic field to pass through the second planar Hall element in asecond direction different than the first direction, wherein the firstand second directions differ by an angle difference in a range of onehundred eighty to one hundred forty degrees. In other embodiments, theangle difference can be in the range of two hundred to forty degrees.

As described above, magnetic flux concentrators described herein canhave a relative magnetic permeability greater than about two.

Referring now to FIG. 11, a current sensor 1100 can include first andsecond planar Hall elements 1106, 1108 disposed over or within a surfaceof a substrate 1104, for example, a semiconductor substrate. Arrows overthe planar Hall elements 1106, 1108 are representative of maximumresponse directions or axes.

An electronic circuit 1110 can also be disposed over or within thesurface of a substrate 1104 The electronic circuit 1110 can be the sameas or similar to the electronic circuit 301 of FIG. 3.

The substrate 1104 can be disposed proximate to or upon a lead frame1102, and electrically coupled to the lead frame with bond wires or thelike.

A magnetic flux concentrator 1114 can be disposed on an opposite side ofthe lead frame 1102. The magnetic flux concentrator 1114 can be like anyof the magnetic flux concentrators described above. A mold compound 1112can encapsulate the substrate 1104, the magnetic flux concentrator 1114,and a portion of the lead frame 1102.

The current sensor 1100 can be disposed proximate to a conductor 1116that can carry a current that is measured by the current sensor 1100.The measured current can be in a direction into or out of the page.

The current sensor 1100 and a current sensor show below in conjunctionwith FIG. 12 are shown to have single in line package (SIP)arrangements. It will be recognized that other package arrangements,e.g., surface mount (SMD) arrangements, are also possible using thesimilar packaging techniques.

Referring now to FIG. 12, a current sensor 1200 can include first andsecond planar Hall elements 1206, 1208 disposed over or within a surfaceof a substrate 1204, for example, a semiconductor substrate. Anelectronic circuit 1210 can also be disposed over or within the surfaceof a substrate 1204 The electronic circuit 1210 can be the same as orsimilar to the electronic circuit 301 of FIG. 3.

The substrate 1204 can be disposed proximate to or upon a lead frame1202, and electrically coupled to the lead frame with bond wires or thelike.

A mold compound 1212 can encapsulate the substrate 1204 and a portion ofthe lead frame 1202. A magnetic flux concentrator 1214 can be disposedproximate to an opposite side of the lead frame 1202 and over the moldcompound 1212. The magnetic flux concentrator 1214 can be coupled to themold compound 1212 with an adhesive.

The current sensor 1200 can be disposed proximate to a conductor 1216that can carry a current that is measured by the current sensor 1200.The measured current can be in a direction into or out of the page.

Referring now to FIG. 13, in comparison with FIG. 4, a current sensorarrangement 1300 includes a magnetic flux concentrator 1306 andpositions 1308, 1310 of planar Hall elements in relation to a bus barconductor 1302. An arrow 1304 is indicative of directions of currentthat can be sensed with the current sensor arrangement 1300.

The magnetic flux concentrator 1306 can be a comprised of a uniformmaterial.

Referring now to FIG. 14, in comparison with FIG. 4, a current sensorarrangement 1400 includes a magnetic flux concentrator 1406 andpositions 1408, 1410 of planar Hall elements in relation to a bus barconductor 1402. An arrow 1404 is indicative of directions of currentthat can be sensed with the current sensor arrangement 1400.

The magnetic flux concentrator 1406 can be a comprised of a plurality ofhigh permeability layers in order to be less impacted by any eddycurrents that may occur within the magnetic flux concentrator 1406compared with the magnetic flux concentrator 1306 of FIG. 13. Asdescribed above, the layers are used to improve the accuracy of thecurrent sensor arrangement 1400 when eddy currents are experienced, i.e.when sufficiently high frequency AC currents flow in bus bar 1302

Layered magnetic flux concentrators can be used in place of any of themagnetic flux concentrators described here.

Referring now to FIG. 15, a current sensor 1500 can include first andsecond magnetoresistance elements 1506, 1508 disposed over or within asurface of a substrate 1504, for example, a semiconductor substrate.Arrows over the magnetoresistance elements 1506, 1508 are representativeof maximum response directions or axes.

An electronic circuit 1510 can also be disposed over or within thesurface of a substrate 1504 The electronic circuit 1510 can include abridge circuit that couples the first and second magnetoresistanceelements 1506, 1508 to generate a differential signal.

The substrate 1504 can be disposed proximate to or upon a lead frame1502, and electrically coupled to the lead frame with bond wires or thelike. The lead frame can include leads 1502 and a mounting plate 1502 b.

A magnetic flux concentrator 1514 can be disposed proximate to an edgeof the substrate 1504. The magnetic flux concentrator 1514 can be likeany of the magnetic flux concentrators described above. A mold compound1512 can encapsulate the substrate 1504, the magnetic flux concentrator1514, and a portion of the lead frame 1502. An alternate arrangementlike the arrangement of FIG. 12 can leave the magnetic flux concentrator1514 outside of the mold compound.

The current sensor 1500 can be disposed proximate to a conductor 1516that can carry a current that is measured by the current sensor 1510.The measured current can be in a direction into or out of the page.

Flux lines will be understood from discussion above to pass through thefirst and second magnetoresistance elements 1506, 1508 with directioncomponents parallel to the arrows that indicate the maximum responsedirections, but in opposite directions.

All references cited herein are hereby incorporated herein by referencein their entirety.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent that other embodimentsincorporating these concepts, structures and techniques may be used.Accordingly, it is submitted that the scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims.

Elements of embodiments described herein may be combined to form otherembodiments not specifically set forth above. Various elements, whichare described in the context of a single embodiment, may also beprovided separately or in any suitable subcombination. Other embodimentsnot specifically described herein are also within the scope of thefollowing claims.

What is claimed is:
 1. A current sensor, comprising: a magnetic fluxconcentrator; a first magnetic field sensing element disposed proximateto the magnetic flux concentrator, the first magnetic field sensingelement having a first maximum response axis, the first magnetic fieldsensing element operable to generate a first signal responsive to afirst magnetic field proximate to the first magnetic field sensingelement resulting from an electrical current passing through aconductor, wherein the magnetic flux concentrator is operable toinfluence a direction of the first magnetic field; a second magneticfield sensing element disposed proximate to the magnetic fluxconcentrator, the second magnetic field sensing element having a secondmaximum response axis, the second magnetic field sensing elementoperable to generate a second signal responsive to a second magneticfield proximate to the second magnetic field sensing element resultingfrom the electrical current passing through the conductor, wherein themagnetic flux concentrator is operable to influence a direction of thesecond magnetic field; and a differencing circuit operable to subtractthe first and second signals to generate a difference signal related tothe electrical current.
 2. The current sensor of claim 1, wherein themagnetic flux concentrator is operable to influence the direction of thefirst magnetic field to pass through the first magnetic field sensingelement in a first direction, and wherein the magnetic flux concentratoris operable to influence the direction of the second magnetic field topass through the second magnetic field sensing element in a seconddirection different than the first direction.
 3. The current sensor ofclaim 2, wherein the first magnetic field sensing element comprises afirst planar Hall element, and wherein the second magnetic field sensingelement comprises a second planar Hall element.
 4. The current sensor ofclaim 3, wherein the first and second maximum response axes are parallelto a common axis.
 5. The current sensor of claim 3, wherein the magneticflux concentrator is operable to influence the direction of the firstmagnetic field to pass through the first planar Hall element in a firstdirection, and wherein the magnetic flux concentrator is operable toinfluence the direction of the second magnetic field to pass through thesecond planar Hall element in a second direction substantially oppositefrom the first direction.
 6. The current sensor of claim 3, wherein themagnetic flux concentrator is operable to influence the direction of thefirst magnetic field to pass through the first planar Hall element in afirst direction, wherein the magnetic flux concentrator is operable toinfluence the direction of the second magnetic field to pass through thesecond planar Hall element in a second direction different than thefirst direction, and wherein the first and second directions differ byan angle difference in a range of one hundred eighty to one hundredforty degrees.
 7. The current sensor of claim 3, wherein the magneticflux concentrator is operable to influence the direction of the firstmagnetic field to pass through the first planar Hall element in a firstdirection, wherein the magnetic flux concentrator is operable toinfluence the direction of the second magnetic field to pass through thesecond planar Hall element in a second direction different than thefirst direction, and wherein the first and second directions differ byan angle difference in a range of two hundred to forty degrees.
 8. Thecurrent sensor of claim 3, wherein the magnetic flux concentrator has arelative magnetic permeability greater than two.
 9. The current sensorof claim 3, wherein the magnetic flux concentrator has a central planebisecting the magnetic flux concentrator, wherein the magnetic fluxconcentrator is substantially symmetrical around the central plane, andwherein the first and second planar Hall elements are disposed onopposite sides of the central plane.
 10. The current sensor of claim 9,wherein the first and second planar Hall elements are equidistant fromthe central plane.
 11. The current sensor of claim 3, wherein themagnetic flux concentrator has a shape and a position selected to resultin the first signal and the second signal being opposite signals havingsubstantially the same amplitude but opposite signs.
 12. A method ofmeasuring an electrical current, comprising: providing a first magneticfield sensing element disposed proximate to a magnetic fluxconcentrator, the first magnetic field sensing element having a firstmaximum response axis; providing a second magnetic field sensing elementdisposed proximate to the magnetic flux concentrator, the secondmagnetic field sensing element having a second maximum response axis;using the first magnetic field sensing element to generate a firstsignal responsive to a first magnetic field proximate resulting from theelectrical current passing through a conductor, wherein the magneticflux concentrator is operable to influence a direction of the firstmagnetic field; using the second magnetic field sensing element togenerate a second signal responsive to a second magnetic field resultingfrom the electrical current passing through the conductor, wherein themagnetic flux concentrator is operable to influence a direction of thesecond magnetic field; and with a differencing circuit, subtracting thefirst and second signals to generate a difference signal related to theelectrical current.
 13. The method of claim 12, wherein the magneticflux concentrator is operable to influence the direction of the firstmagnetic field to pass through the first magnetic field sensing elementin a first direction, and wherein the magnetic flux concentrator isoperable to influence the direction of the second magnetic field to passthrough the second magnetic field sensing element in a second directiondifferent than the first direction.
 14. The method of claim 13, whereinthe first magnetic field sensing element comprises a first planar Hallelement, and wherein the second magnetic field sensing element comprisesa second planar Hall element.
 15. The method of claim 14, wherein thefirst and second maximum response axes are parallel to a common axis.16. The method of claim 14, wherein the magnetic flux concentrator isoperable to influence the direction of the first magnetic field to passthrough the first planar Hall element in a first direction, and whereinthe magnetic flux concentrator is operable to influence the direction ofthe second magnetic field to pass through the second planar Hall elementin a second direction substantially opposite from the first direction.17. The method of claim 14, wherein the magnetic flux concentrator isoperable to influence the direction of the first magnetic field to passthrough the first planar Hall element in a first direction, wherein themagnetic flux concentrator is operable to influence the direction of thesecond magnetic field to pass through the second planar Hall element ina second direction different than the first direction, and wherein thefirst and second directions differ by an angle difference in a range ofone hundred eighty to one hundred forty degrees.
 18. The method of claim14, wherein the magnetic flux concentrator is operable to influence thedirection of the first magnetic field to pass through the first planarHall element in a first direction, wherein the magnetic fluxconcentrator is operable to influence the direction of the secondmagnetic field to pass through the second planar Hall element in asecond direction different than the first direction, and wherein thefirst and second directions differ by an angle difference in a range oftwo hundred degrees to forty degrees.
 19. The method of claim 14,wherein the magnetic flux concentrator has a relative magneticpermeability greater than two.
 20. The method of claim 14, wherein themagnetic flux concentrator has a central plane bisecting the magneticflux concentrator, wherein the magnetic flux concentrator issubstantially symmetrical around the central plane, and wherein thefirst and second planar Hall elements are disposed on opposite sides ofthe central plane.
 21. The method of claim 20, wherein the first andsecond planar Hall elements are equidistant from the central plane. 22.The method of claim 14, wherein the magnetic flux concentrator has ashape and a position selected to result in the first signal and thesecond signal being opposite signals having substantially the sameamplitude but opposite signs.